Method and apparatus for printing

ABSTRACT

A method and apparatus for printing intelligence on a surface by the use of short pulses of visible light energy impinging on a coating formed of a colorant and an absorber of radiant energy. A stack is formed including a sheet of material having transparent areas, a coating made up of the colorant and energy absorber and a surface to be printed. A burst of light is caused to pass through the transparent areas of the sheet material causing momentary heating of the exposed areas of the coating and volatilization of the colorant in the exposed areas followed by immediate condensation of the colorant on the printing surface immediately adjacent the coating. The colorant transference corresponds exactly to the shape of the transparent areas in the sheet of material.

United States Patent 11 1 Kinney et al.

[ Dec. 24, 1974 v [22] Filed:

[ METHOD AND APPARATUS FOR PRINTING [75] lnventorsz Layton C. Kinney,Chicago; Edwin H. Tompkins, Riverside, both of Ill.

[73] Assignee: American Screen Process Equipment Company, Chicago, 111.

52 U. S.Cl 101'/471","96/27 11,250/3171 [51] Int. Cl B41m 5/00 [58]Field of Search 117/36.1; 250/65 T; 101/470, 471, 493; 96/ 27 R [56]References Cited UNITED STATES PATENTS 3,121,162 2/1964 Roman et al250/65 T 3,219,818 11/1965 Luebbe 250/65 T 3,280,735 10/1966 Clark etal. 250/65 T x 3,455,687 7/1969 HOlStBfld et al. 250/65 T x 3,476,57811/1969 Brinckman 250/65 T x Primary Examiner-David Klein Attorney,Agent, or Firm-Stone, Wagner & Aubel,

[5 7] ABSTRACT A method and apparatus for printing intelligence on a Isurfaceby, the use of short pulses ofvisible light onergy'impinging on acoating formed-of a colorant and an absorber of radiant energy. A stackis formed including a sheet of material having transparent areas, acoating made up of the colorant and energy absorber and a surface to beprinted. A burst of light is caused to pass through the transparentareas of the sheet material causing momentary heating of the exposedareas of the coating and volatilization of the colorant in the exposedareas followed by immediate condensation of the colorant on the printingsurface immediately adjacent the coating. The colorant transferencecorre-.

sponds exactly to the shape of the transparent areas in the sheet ofmaterial.

9 Claims, 3 Drawing Figures METHOD ANDAPPARATUS FOR PRINTING beconveniently termed relief or letter press printing, in

which the printing surface is in relief above the nonprint'ing parts,planographicprinting, in which the printed material is transferred, forexample; by photog- 'raphy, to' a single plate and printed from an evensurface; and intaglio prin'ting'in which the parts which are to beprinted are cut into the plate below the plate surface. Each ofthesetypes of printing operations ini of radiant energy and may take theform of a photoflash particular configuration which is'to be printedonto a printing surface is present in the mask either in the form of atransparent area 17 desired shape. 1

The second element of theprinting plate is in the form of a layer orcoating 18 of colorant and a radiant energy absorber such as carbonblack. The coating 18 can be formed onthe underside of the photographicor'by a cutout 19 of the transparency or alternatively it can be formedon a transparent sheet 20 (FIG. 2) and positioned adjacent volv'es thepreparation of a printing plate of the appropriate type. Printing platesare normally of a heavy permanent construction usually metal and areformed originally by some transferal process of an image from costs forshort runs as well as delays in theavailability of a plate for theprinting process.

The present invention'avoids the cost and delays encountered in theprior art by the elimination of the conventional printing plate. It isdirected to a printing process in whichamask in the form ofa'photographic transparency or stencil is employed in combination with acoating as a printing plate. The mask is employed directly in theprinting process'and is not destroyed by the printing operation, and canbe reused an unlimited number of times without changing its basiccharacter. Due to a saving in weight, the printing presses employing thepresent invention'can also be made of lighter construction since themass of the printing plate will not be so great as to cause vibrationsand, misalignment in the remainder of the apparatus at highspeedsu i 3It is an object of the'present invention to provide a novelprocess for'theprinting of intelligence on a surface.-

1 Another object of the present invention is to provide a low cost highspeed printing process without the necessity of employinga conventionalprinting plate.

Still another object of the present invention is to provide a low costprinting plate.

These and other objects of the present invention will become evidentfrom the following description in connection with the drawings, inwhich:

FIG. I is an elevational'view partially in section of an apparatusembodying the present invention;

FIG. 2 is an explodedperspective view of'an alternate forrnof theapparatus illustrating the present invention; and

FIG. 3 is a sectional view of the apparatus taken along line 33 of FIG.2 and showing the elements in assembled form. The invention isillustrated in the drawings in two different embodiments of apparatususeful in performing a the improved process. Each arrangement shown inthe drawings has a source l0'of radiant energy (shown only in FIG. 1)preferably in the visible light range of wavelength. The source iscapable of delivering short pulses the underside of the mask with thetransparent sheet interposed betweenthe maskand the. coating. Theforegoing two elements constitute the printing plate 12 and 12a of thepresent inventionand'a're placed with the coating in contact with thesurface of a printing mediun'1 22, normally paper, in the path ofradiation from thesource of radiant energy.

The radiant energy source is flashed briefly causing energy to impingeon the entire surface of the mask. Some of this energy is blocked by thenontransparent areas of the mask while the remainder passesthrough thetransparent areas and momentarily heats the coating in the correspondingarea due to' the radiant energy absorber contained therein. Thecolorant, usually in form the printing plate.[ It should be understoodthroughout that the term mask is used for convenience only and may referto either a photographic transparency, a stencilor other types oftransparencies. In addition, the term colorant willbe usedinterchangeably with the term dye; however, the substances which can beutilized as colorants are not limited to dyes in the conventional use ofthe term dye.

FIG. 1 illustrates the source .of radiant energy 10 which in thepreferred embodimet takes the form of an electronic flash lamp. The lampis required to provide the input'of radiant energy to cause thevolatilization of the colorant from the coating formed on thetransparency. The pulse of light which is required to perform theprocessoffthe present invention is typically very short, of the order ofmilliseconds, and the'total energy incident on the surface of thephotographic transparency is of the order of 20. joules per square inchfor the typicalcolorant.

The exact duration and. energy level of the light source is one of agreat number of variables in the pro cess of the present inventionwhich, similar to photography, can be manipulated to achieve the desiredresult. Specifically, the energy required is a function of the thicknessof the coating, the transparency of the thermal conductivities of thecolorant and transparthe particular colorants which may be employed andthe thermal conductivities of the colorants and the transparencies usedare well known by persons skilled in this art and are also readilyavailable from standard or light absorbing portion of the coating andwithout sufficient heating of the coating under the opaque areas of themask to permit vaporization of the dye present on'that portion of thecoating. The present invention operates on a .principle of differentialheating of the coating below the, transparent and nontransparent areasof the mask. Accordingly, a long term low energy level source of lightenergy might result in the destruction of the mask orin the vaporizationof the entire surface of the coating rather than just the area adjacentthe transparent portion of the mask.

Since it isthe relative transparency of the two portions of the mask tovisible light which makes the operation of the present process possible,it is preferred that the preponderance of the energy employed in thepresent invention be, visible light because the efficiency oftransmission and blocking of the light by the transparent areasgradually drops as one approaches and enters either the infrared orultraviolet wavelengths. Accordingly, differential heating is easiest toobtain with visible light. j

The mask as stated earlier may be in the'form of an ency. The values ofthe latent heats of vaporization of able so that the coating will heatsufficiently under the brief pulse of light to cause the vaporization ofthe volatile portion of the coating. Examples of typical colorantemployed in the present invention include Victoria green, fuchsin,manganic acetyl acetonate, crystal violet,;Victoria blue,.Du Pont oilblue A, Saphranine T, and Rhodamine 5 GDN. The colorant employed shouldvaporize without decolorizing or decomposing and should, not setoff ontothe printing surface upon contact at room temperature. In order toprovide additional structural strength to the coating, a binder such assilicone resin is preferably employed for most comings to cause thecarbon portion of the coating to adof energy absorber and binder whichis subsequently spray coated with the desired colorant. This type ofcoating provides the advantage of being rechargeable withoutrestructuring the carbon phase of the coating. In other words, if theplate is mounted in a rotary printing press, after each use of the platein the printing process, an additional film of colorant is sprayed onthe outer surface of the carbon black coating for use in the subsequentprinting operation. a

The other basic approach is the incorporation of the colorant or dyewith the energy absorber and the binder directly .into the coating sothat the particles of dye are interspersed throughout the coating.This-approach might be employed for short runs in which a a smallmultiple of prints would be made without reordinary photographicpositive or negativel4 having the desired design as a transparent areaboundedby nontransparent areas and may be glass mounted. The transparentarea permits the light energy to pass through while thenontransparentar'eas block the light. The result is selective heating ofthe'coating beneath the transparent area. In this connection translucentareas are suffi'ciently inefficient to be regarded as nontransparent forpurposes of the present invention.

The nontransparent area of the mask is normally dark in color andabsorbs energy itself. Due to the shortness of the burst of light,however, the nontransparent area does not heat sufficiently to cause thecoating beneath it to heat to the volatilization temperature of thecolorant. If in using a particular colorant the heat tends tocause'slight volatilization under the nontransparent'areas of the mask,these areas can be coated with a radiation reflective substance toreduce heating. If instead of a photographic transparency the stencil 16is employed, the foregoing remarks still apply except that the coating18 is applied to a separate transparent sheet of material such as Mylar.The reason for this difference is that the transparent areas 19 of thestencil are cut out andprovide no surface to which the coating may beapplied.

The. coating can take many forms though it is preferredthat it contain acolorant substance which volatilizes without decomposition at relativelylow temperatures and that it contain a radiant energy absorber such ascarbon black. The radiant energy'absorber is desircharging the coating.

The coating may be formed as in FIG. 1 integrally on the surface of themask or alternatively on the surface of' a totally transparent substrate20 which is then placed against the/mask (FIGS. 2 and 3). Thedirectcoating provides the advantage of little or no loss, of sharpness in thetransfer of the image from the photographic transparency to the printingpaper. The second approach has the-advantage of not contacting the maskwith the'coating and only results-in a'slight loss of sharpnessdependingon the thickness of the transparent sheet upon which thecoating is formed. The loss of sharpness is due primarily to thescattering of light at the boundaries of the transparent areas due tothe thickness of the transparent sheet.

The coating may be formed by brushing, rolling or spraying andisaccomplished by use of-a solvent such as toluene mixed with theconstitutents of the remainder of the coating which are pulverized ormilledin powder form. The application of the coating should be done withcare because of the need for uniform thickness throughout the coating.This need is due in part to v the vaporization ofithe dye material whichrequires a certain temperature for each particular dye and which willoccur only in the areas where that temperature is achieved. It istherefore possible that having the coating of uneven thickness or toothick overall may result in insufficient heat being conducted to thesurface adjacent the printing paper resulting in an inferior print Theprinting medium employed in the basic process may be sheet material 'ofany type and'not be specially treated. Certain variations which will bedescribed hereinafter do involve, however, the treating of the paper aswell as an optional step of developing an image with steam.

In'the operation of the present invention it is possible that some ofthe binder may also volatilize with the dye.

Accordingly, the binder employed is preferably colorless although it'might alsobe colored if it does not volatilize or may be entirely absentfrom some coatings.

The system of the present invention lends itself to .multicolor printingas well as single color printing. One

ond'mask having are as complementary to the already printed areas is putin its place. The coating on this maskutilizes the other-color dye to beemployed and the mask is placed over the same paper and the light isagain flashed at an energy level sufficient to vaporize the second dyewhich in turn condenses on the desired portions of the paper resultingin a two color print. Ob-

viously, this operation could be extended to as many colors as desiredwithout departing from the scope of the invention.

An added feature which can be achieved by the use of a first mask andasecond mask having mutual transparent areas is a three color printwhere the dye of the first mask and the second mask mixes in these areascreating a secondary color. For example, a blue dye and a yellow dyecreate a green area.

In still another embodiment of the present invention a' transparentsheetof material is coatedwitha coating containing two distinct colorantshaving different latent heats of vaporization contained within thesinglecoating. A first mask having a portion of the areato be printed intransparent form is then placed against the coating and thelight isflashed to an energy level sufficient to vaporize one butnot bothofthecolorants. The

mask is removed and a second mask is employed having complementary areasto the areas of the first mask. The light is again flashed this time atan energy level sufficient to vaporize both of the colorants. Theresultant print is atwo color print having a first color correspondingto the lower latent heat of vaporization colorant and a second colorcorresponding to the mix of the lower and higher colorants which havevolatized at the same time.

As mentioned earlier the paper employed in the presentinvention isnormally untreated. It is possible, however, to treat the paper with animpregnation or coating of a chemical and to condense the dye or othermaterial onto the surface of the paper causin'gan image to appear due tothe interaction of the twomaterials or by subjecting the paper to afurther step to develop the latent print. One example of such systemincludes the impregnation of paper with ferric ammonium sulfate and theuse of tannic acid in place of the dye in the coating on the mask. Thetannic acid is caused by the photoflash vto vaporize and condense on thepaper. The resulting blue black iron tannate image is developed bybriefly subjecting the print to steam.

The present invention will be better understood with reference to thefollowing examples.

EXAMPLE I A mixture of 7.59 parts silicone resin binder (GE SR-8 0),0.59 parts carbon black and toluene was milled for 24 hours ina ballmill. Additional toluene .was added until the, mixture was of asprayableconsisfrom the surface of the negative and was flashed. The

energy at the surface of the negative was approximately 20 joules persquare inch. The resultant print was an exact reproduction of thetransparent areas of the negative and the negative was not damagedduring the creation of the print. EXAMPLEII The preparation of thephotographic negative was as set forth in Example I. The paper in thiscase was impregnated with ferric ammonium sulfate, and the black coatingof the transparencywas sprayed with an alcohol solutio'n'of tannic acid.After the acid was dried the assembly was subjected to photoflashradiation. The resultant blue black iron tannate image was developed bybriefly subjecting the print to steam. The resultant print showed highfidelity to the original.

EXAMPLE n The steps of Example I were followed precisely except that thedye employed was fuchsin.

EXAMPLE IV The steps of Example I were followed precisely except thatthe dye employed was crystal violet.

Other prints were made employing the steps of Example I and substitutingas dyes the following-materials: Victoria Blue, and Du Pont dyesRhodamine 5 GDN, Saphranine T, and oil blue A. In each case'theresultant print was clear and showed high fidelity to the original.

EXAMPLE v The transparency was prepared in accordance with Examples Iand II and the paper was prepared in accor dance with Example II. Thetransparency 'was then sprayed with gallic acid and the image wasdeveloped by subjecting the paper briefly to steam.

I EXA PLE V! v A composition was prepared containing 0.5 parts carbonblack and 2.0-parts manganic acetyl acetonate and toluene. The mixturewas ball milled for 24 hours. Additional toluene was added to permitspraying and the solution was sprayed on the emulsion side of a glassmounted transparency to the point of incipient opacity and dried in themanner described in Example I.

The exposure to photoflash energy was also accomplished in the samemanner'as set forth in Example I. The resultant image was brownishblack. In this exam ple no binder was required since the manganesecomplex forms a coherent adherent film which prevents in- EXAMPLE vii Aglass mounted negative-was sprayed with athin coat of silicone resinwhich was then cured by heating for 48 hours at 120C. A compositionconsisting of 1.6

parts Victoria blue, 2.0parts carbon black and 1.0

EXAMPLE VIII The following composition was milled in accordance withExample I: Paraffin wax 2 parts; Victoria blue lv part; carbon black2.parts; and toluene. The mixture was heated to dissolve the wax priorto the milling operation. Additional toluene was added to achieve sprayconsistency and the spray coating was applied to a transparent Mylarsheet until opacity was reached. After drying as in Example I coatedfilm was placed in contact with paper and was overlaid with a negativetransparency=The assembly was placed in a contact printing frame andsubjectedto flash energy as described previously. A blueprint of goodresolution was produced.

EXAMPLE 1X sharpness.

EXAMPLE X The composition of Example IX was mixed to sprayingconsistency and the spray coating was applied to a transparent Mylarsheet until opacity as reached after drying as in Example I. The coatedfilm was placed in contact with paper and was overlaid with a negativecorporated carbon black from rubbing off the coating.

transparency. The assembly was placed in a contact] printing frame andsubjected to flash energy as described previously. A blue print of goodresolution was produced.

The prints formed in the preceding examples were each tested for set offby being inserted into a book and subjected to the normal pressure ofa-closed book. No appreciable set off was observed on the facing pagesafter a period of several months. a

While the foregoing description has been presented with reference toparticular materials and configurations, these are presented by way ofexample only and not by way of limitation. The present inventionincludes other embodiments within the scope of the following claims.

We claim: I v

l. A method of printingintelligence on a surface of a printing mediumcomprising steps of:

formingv a layer comprising a volatilizable colorant andan absorber ofradiant energy,

positioning said layer between the surface tonbe printed and a sheet ofmaterial having an area transparent'to radiant energy and correspondingto the intelligence to be printed, and subjecting said sheet of materialand the portion of said layer adjacent said transparent area to a pulseof radiant energy sufficient to cause said colorant in said area tovolatilize under the influence of .the radiant energy absorbed bysaidabsorber of radiant energy and to condense on said surface to be.

I printed.

2. A method as set forth in claim 1 wherein said layer is a coating andis formed on the surface of 'saidsheet of material.

3. A method asset forth in claim 1 further comprising the steps offorming said layer as a coating on a transparent substrate andpositioning said substratebetween said sheet material and said surfaceto be printed.

Amethod as set forth in claim 3 wherein said sheet material is a stencilhaving cutout areas corresponding to said intelligence to permit saidradiant energy to pass through said substrate to said layer.

5. A method asset forth in claim 1 wherein forming said layer comprisesthe steps of:

. mixing colorant, radiant energy absorbent material and a binder with asolvent, applying the resultant mixture to one surface of said sheet ofmaterial to form'a coating, and driving off the solvent withoutdisrupting said coat- 6. A method as set forth in claim 1 wherein saidlayer and said sheet material 'are employed for multiple prints,said'method including the steps of providing successive surfaces to beprinted adjacent said layer, and

subjecting said sheet of material to successively stronger pulses ofradiant energy for each successive surface to be printed whereby saidcolorant'is partially volatilize'd by each successive pulse.

7. A method asset forth in claim 1 wherein the strength of said pulse ofradiant energy on said sheet of material is of the order of 20 joulesper square inch.

8. A method of printing intelligence onto a surface of a printing mediumcomprising the steps of:

forming a first-layer having a firstdye and an ab,-

sorber of radiant energy, positioning saidfirst layer between saidsurface to be printed and a first sheet of material having a first areatransparent to radiant energy and corresponding to a first .portion ofthe intelligence to be printed, subjecting said first sheet of materialand the portion of said first layer adjacent said first transparent areato a pulse of radiant energy effective to cause said first dye in saidarea to volatilize under the influenceof the radiant energy absorbed bysaid absorber of radiant energy and to condense on said surface to beprinted, I forming a second layer comprising a second dye and anabsorber or radiant energy, positioning said second layerbetween saidsurface to be printed and a second sheet of material having a secondarea transparent to radiant energy and corresponding to a second portionof the intelligence to be printed, and subjecting said second sheet ofmaterial and the portion of said second layer adjacent said secondtransparent area to a pulse of radiant energy effective to cause saidsecond dye in said second area to volatilize due to the influence ofradiant energy absorbed by said absorber of radiant energy and tocondense on said surface to be printed. 9.'A method of printingintelligence onto a surface of printingmedium comprising the steps of:

forming a layer comprising a first colorant, a second colorant, and anabsorber of radiant energy, said first colorant and said second coloranthaving different latent heats of vaporization,

, positioning said layer between the surface to be printed and a firstsheet of material having a first area transparent to radiant energy andcorresponding to a first portion of the intelligence to be printed,subjecting said first sheet of material and the portion of said layeradjacent said transparent area 'to a pulse of radiant energy ofsufficient strength to volatilize under the influence of the radiantenergy abstrength to volatilize said second colorant under the influenceof the radiant energy absorbed by said absorber of radiant energy.

1. A method of printing intelligence on a surface of a printing mediumcomprising steps of: forming a layer comprising a volatilizable colorantand an absorber of radiant energy, positioning said layer between thesurface to be printed and a sheet of material having an area transparentto radiant energy and corresponding to the intelligence to be printed,and subjecting said sheet of material and the portion of said layeradjacent said transparent area to a pulse of radiant energy sufficientto cause said colorant in said area to volatilize under the influence ofthe radiant energy absorbed by said absorber of radiant energy and tocondense on said surface to be printed.
 2. A method as set forth inclaim 1 wherein said layer is a coating and is formed on the surface ofsaid sheet of material.
 3. A method as set forth in claim 1 furthercomprising the steps of forming said layer as a coating on a transparentsubstrate and positioning said substrate between said sheet material andsaid surface to be printed.
 4. A method as set forth in claim 3 whereinsaid sheet material is a stencil having cutout areas corresponding tosaid intelligence to permit said radiant energy to pass through saidsubstrate to said layer.
 5. A method as set forth in claim 1 whereinforming said layer comprises the steps of: mixing colorant, radiantenergy absorbent material and a binder with a solvent, applying theresultant mixture to one surface of said sheet of material to form acoating, and driving off the solvent without disrupting said coating. 6.A method as set forth in claim 1 wherein said layer and said sheetmaterial are employed for multiple prints, said method including thesteps of providing successive surfaces to be printed adjacent saidlayer, and subjecting said sheet of material to successively strongerpulses of radiant energy for each successive surface to be printedwhereby said colorant is partially volatilized by each successive pulse.7. A method as set forth in claim 1 wherein the strength of said pulseof radiant energy on said sheet of material is of the order of 20 joulesper square inch.
 8. A method of printing intelligence onto a surface ofa printing medium comprising the steps of: forming a first layer havinga first dye and an absorber of radiant energy, positioning said firstlayer between said surface to be printed and a first sheet of materialhaving a first area transparent to radiant energy and corresponding to afirst portion of the intelligence to be printed, subjecting said firstsheet of material and the portion of said first layer adjacent saidfirst transparent area to a pulse of radiant energy effective to causesaid first dye in said area to volatilize under the influence of theradiant energy absorbed by said absorber of radiant energy and tocondense on said surface to be printed, forming a second layercomprising a second dye and an absorber or radiant energy, positioningsaid second layer between said surface to be printed and a second sheetof material having a second area transparent to radiant energy andcorresponding to a second portiOn of the intelligence to be printed, andsubjecting said second sheet of material and the portion of said secondlayer adjacent said second transparent area to a pulse of radiant energyeffective to cause said second dye in said second area to volatilize dueto the influence of radiant energy absorbed by said absorber of radiantenergy and to condense on said surface to be printed.
 9. A method ofprinting intelligence onto a surface of printing medium comprising thesteps of: forming a layer comprising a first colorant, a secondcolorant, and an absorber of radiant energy, said first colorant andsaid second colorant having different latent heats of vaporization,positioning said layer between the surface to be printed and a firstsheet of material having a first area transparent to radiant energy andcorresponding to a first portion of the intelligence to be printed,subjecting said first sheet of material and the portion of said layeradjacent said transparent area to a pulse of radiant energy ofsufficient strength to volatilize under the influence of the radiantenergy absorbed by said absorber of radiant energy said first colorantadjacent said first transparent area, substituting a second sheet ofmaterial for said first sheet of material said second sheet of materialhaving a second area transparent to radiant energy and corresponding toa second portion of the intelligence to be printed, and subjecting saidsecond sheet of material and the portion of said layer adjacent saidsecond transparent area to a pulse of radiant energy of sufficientstrength to volatilize said second colorant under the influence of theradiant energy absorbed by said absorber of radiant energy.